Input collector system for electrical amplifiers



Nov, 11, 1930. H, A, SNOWET AL INPUT COLLECTOR SYSTEM FOR ELECTRICAL AMPLIFIERS Filed Sept. 6, 1928 gwmwltou;

Patented Nov. 11 1930 Lamas? Urrsn stares V'PAIATENT oFFicE.

HAROLD A. SNOW AND} WILLTAM D. LOUGI'ILIN, OF BOON TON, JERSEY, ASSIGNORS T0 RADIO FREQUENCY LABCRATORIES, INCL, OF BOON TON, NEW JERSEY, A CORPO- RATION OF NEVT JEBSEY INPUT COLLECTOR sysrnn non nLnc r'nIcAn AMPLIFIERS Application filed September 6, 1928. Serial No. 304,276.

This invention relates to electrical amplifier circuits, and more especially to an improved input and collector system for such amplifier circuits, and constitutes an 1mprovement on the input system described and claimed in the copending application of Frederick H. Drake and William D. Loughlin, Serial No. 285,886, filed June 16, 1928. It is particularly applicable to an input and collector system for a radio frequency amplifier suitable for use in radio rece1v1ng sets, and the invention will hereafter be described in connection with such an ampliher, in which connection it has many advantages. g

An object of the invention is to provide such an input system includin an electromagnetic collecting deviceor loop, and an optional connection to a supplementary elec-V trostatic collecting device or antenna. A further object is to combine such a collectorsystem with an input system constituting a desirable means for coupling said collecting devices to a radio frequency amplifier with which the system is associated. A further object is to provide such an input-collector system including a volume control. Other objects oftheinvention will appear'from the following description:

In the accompanying drawings, the single figure shows a multi-stage radio frequency amplifier including an mput and collector system according to the present invention.

Referring nowto the" drawings, the multistage radio frequency amplifier comprises the four vacuum or'audion-tubes T T T and T working into detector tube'T .Each of the amplifier tubes is provided with an anode and an electron-emitting cathode or filament'F. The latter may be heated either by direct or alternating current,-and is here shown as being of the alternating current type by way of example. Theyare supplied from any suitable alternating current source,

and may for example be provided with centre tap resistance R0, by-passedto ground at each end by by-pass condensers C. A bias ing resistance B may also be employed in order to impart the desired bias tothe grids by a common 1s provided with agrid condenser Cg and a Its plate circuit includes G. The detector tube T is provided with a plate P and grid G, but, by way of example, is shown as having a cathode composed of an electron-emitting element F, and a separate heater element H,heated by alternating current. The several tubes are linked or coupled together in this multi-stage arrangement by, means of a balanced network" comprising transformer primary coils L secondary coils L zero-coupled balance coils L balance condensers C and tuning condensers C as described and claimed in United States Patent No. 1,672,811 to Lewis M. Hull. The tuning condensers Cgaresuitably arranged as units of a control. The detector tube T leak resistance Rg. the large condenser C and choke coil or audio transformer primary L. It may operate into a suitable audio frequency amplifier or reproducing device, as desired.

I The foregoing radio frequency amplifier anddetector system is described by way of does enter. into thepr'esent invention as an.

element of a combination. Other radiofrequency amphfier systems may, of course be employed 1n combination with an input-collector system according to the present invention. 7 a

The input-collector system comprises series circuit including a relatively large fixed gang, and-are tuned together con lin condenser Cm variable or trim-v ming inductance L0, an electromagnetic C01,

lecting device La, ordinarily in the form of a loop or similar arrangement, anda tuning condenserfCo. The junction of the fixed coupling condenser Cm and the tuning condenser C0 is at ground. The terminal A is located between the coupling condenser Cm and the trimming inductance L0, and is adapted to have an electrostatic collecting device or antenna connected thereto, as indicated, as by means of switch S, in certain 7 cases. Thus the collecting system always in eludes the electromagnetic collecting device or loop La,

include a supplementary electrostaticcollector or antenna Connected to theterminal A,

'incases where sufficient signal energy .is'not picked upby, the deviceLa. s 3 V V ,Anelectromagneticcollectoror'loopis n"; 7,

"many re. pects adesid'eratum froma practical viewpoint, since, for example, it may be built such 'for example as the interior of a steel building, theloop failsto function satisfactorily and it becomes ployed methods of providing for thischange Y sti'tutionof input systems to the grid, G, of the'first tube,

desirable to augment the collector structure;

a While these facts have been recognized in 1 a general way" in the art,"the hitherto emactual manual subv p or elaborate switching schemes for making this change; Such arrangements are unsatisfactory in that they -ta're costly, cumbersox'ne, and unless carefully have comprised either an designed may the performance: ofthe receiver; a a I 1 a,

The input-collector system according to the present invention provide'sfor a se1r-conftained collecting system within the receiver cabinet and a simple means for'a'ugmenting the collecting system when local conditions demand it.

by the potentiometer, R, connected acrossthe tuning condenser C0, and provided with a variable tap, 1, connected side of the tuning condenser C0 and ground,

it affords aineans for applying any desired portmn from Zero up to the maxlmummf the desirable form than lhas been hitherto obpotential E0 across 'the input'tuning condenantenna, and is ser between 'theigrid andcathode of the first tube, T of the radio frequency amplifier.'

It therefore furnishes an ideal'volunie control, is "available whether the collector Iict'jis used alone or in con unctio-n withthe external ly accompanying volume controls applied to Cm =1000 i farads .-G0 400fL,lL farads (max) 'alternating current tubes; j

Vi e have found that the following constants for an input-collector system according to the present "invention give very sat sfactory results, althoughthey are merely given byway of example, and may be considerablyvaried.

IB=2000O00hms P which is permanently connected V- in series in the input circuit, and may also i it isfimportant- 'to v A volume control is provided, according to the present invention,

Since this i, otei iometer 1S connected between the high, lengths. AS a the wavelength characteristic ofthe input system employing an antenna is of more-V thewavelength range. I V x In addition to the advantagesalready decollector'system as a c'ouplingto' a radio fre- V andas one tuned circuit of quency amplifier,

it will be observed that the such anamplifier,

total tuning c capaclty v of, the input system, witht-he antenna removed, is

pifiiafin y 0 +(7 a 0m" 1 The antenna capacity, when the antenna or tively in parallel with C and acts to increase the effective value of C zin the above equation. I Q r If C is large compared with C as is the electrostatic. collector is employed, is ,effec-f case When the circuit is tuned to short wave J lengths, the term +g approaches 1", band" 5 thetuning capacity Cgis substantially equalto the capacity of the tuning condenser C Since an important application of the in ventionis to arrangements in which the input tuning condenser C ls'one unit ofa gang of condensers operated by a single control,

amen? or re'nain v I L-C products of, the other tuned circuits,

so that all of thetuned circuits tune to resO-f snance together and it willbe seen, that this is have the pr oduct rL fc c in ,alinement with] the (re; is neg-ligibleyin comparison. with 1 for example at short -At the same time,'at short. wavelengthsthe voltage, a betweenantenna and ground, when the antenna isemployed, V

.yis appliedgto the tuned circuit L5 O-om'by {meansof'the coupling betweenithe circuitand the antenna through the capacity C C in being fixed, this coupling decreases at short wavelengths, and increases at long Wave result of this arrangement,

,tainable,andiby proper-proportioning of the "constants of this circuit, the wavelength char- 7 acteristic may be made uniform or'substanf fi- 'th bbj c tg usuap i follows that athecharacterflo'f the performance of the; receiving set is not substantially alteredwhenthe antennaiis employed to sup-I plement the loop,;andjthat the signalenergyij approximately I uniformly augmented o scribed as resulting fromaniinput system so ,applied to the radio frequency amplifier is fly 'necessary'with other arrangements,-v and-43 this results in extreme ease in tuning to different Wavelengths, and in picking up different broadcast stations with a radio receiving set embodying the arrangement. When the volume control is changed the resultant detuning of the system is very small. It is an easy matter to accommodate the system to difierent types and sizes of antennas which may be employed to supplement the loop. At short Wavelengths the coupling of the input system to an antenna is Weak, which is desirable, as pointed out above, since excessive amplifications are not required at short wavelengths. Moreover, the selectivity of the system is high at short wavelengths, where an ordinary radio frequency amplifier is ordinarily relatively nonselective.

Other advantages of an input system according to the present invention will have appeared from the foregoing description, and

the invention is not limited to the particular arrangements or constants herein shown or described, but extends to many variations and modifications thereof, and is limited only by the teachings of the foregoing specification, bythe prior art, and by the following claims.

WVe claim: v

1. An input-collector system for a radio frequency amplifier comprising, in combination, a series circuit including an inductance, a coupling condenser connected to ground, a tuning condenser, an electromagnetic collect ing device, and means for connecting a supplementary electrostatic collecting device across said coupling condenser.

2. An input-collector system fora radio frequency amplifier, comprising a series circuit including an inductance susceptible of a trimming variation, a fixed cou ling condenser connected to ground, a va-ria le tuning condenser, and an electromagnetic collecting device; and means for optionally connecting an electrostatic collecting device to said se-. ries circuit in such a manner as to supplement said electromagnetic collecting device, said coupling condenser having a capacity of an order higher than that of the maximum capacity of the said tuning'condenser.

3. An input-collector system for a radio frequency amplifier, comprising a series circuit including an inductance susceptible of a trimming variation, a fixed coupling condenser connected to ground, a variable tuning condenser, and an electromagnetic collecting device; and an electrostatic collecting device arranged for optional connection to said series circuit in such a manner as to supplement said electromagnetic collecting device, said coupling condenser having a capacity of an order higher than that of the maximum capacity of the said tuning condenser.

4. An input-collector system for a radio frequency amplifier, comprising a series circuit including a trimmable inductance, a fixed coupling condenser, a variable tuning conrived from said electromagnetic collector alone or from said electromagnetic and electrostatic collectors in combination.

5. An input-collector system for a radio frequency amplifier comprising, in combina-. tion, a trimmable inductance, a fixed coupling condenser connected to ground, an electromagnetic collecting device, means for the optional connection to said circuit of an electrostatic collecting device, a variable tuning condenser, and a potentiometer connected across said tuning condenser and provided with a variable tap adapted for connection to the grid of the first tube of a radio frequency amplifier.

6. A radio frequency receiving system comprising, in combination, a multi-stage .radio frequency amplifier, aninput-collector system comprising a'series circuit including a trimmable inductance, a fixed coupling condenser, an electromagnetic collecting device,

and means for the optional connection to said circuit of a supplementary electrostatic collecting device; and volume control means for applying to said radio frequency amplifier a variable portion of the total potential in said input-collector system Whether said potential be derived from said electromagnetic collector alone or from saidelectromagnetic and electrostatic collectors in combination.

In testimony whereof, we aflix our signa tures.

HAROLD A. SNOW. WILLIAM LOUGHLIN. 

